1. Field of the Invention
The present invention relates to a technique for automatically generating an effect tone representing a scene.
2. Description of the Related Art
Conventionally, when effect tones such as the murmur of a brook, the chirping of a bird, and the like, representing a forest scene are to be listened to, a magnetic tape or record disk which records such tones in the forest is reproduced using an audio system. The effect tones also include tones representing a seashore scene, street scene, concert hall scene, and the like. These effect tones are reproduced solely or in synchronism with an image or music, thus creating a scene.
However, in a conventional effect tone generating apparatus, the effect tones recorded on a magnetic tape or record disk have a limited duration, and cannot be reproduced for a long period of time. For example, the chirping of a bird cannot be obtained at a desired timing. It is not also easy to quickly switch effect tones from an ocean scene to a forest scene in synchronism with a TV image. In addition, the entire system becomes bulky, and requires a mechanical portion. Thus, maintenance is necessary.
An electronic musical instrument which generates an effect tone using sampled tones is known (a keyboard instrument "SX-K700" is available from Technics, Japan). Since this electronic musical instrument has a limited sampling time, it performs loop reproduction. Thus, changes in tone are little, and the reproduced tones sound monotonous due to monaural reproduction.
As another function of an electronic musical instrument, in order to obtain a fade-in/fade-out effect for automatically increasing/decreasing a tone volume, control using a VCA (voltage controlled amplifier) or a fader (volume) with a motor is required.
Such automatic tone volume control allows one to naturally add effect tones to music or image.
However, in the above-mentioned tone volume control, in, e.g., an electronic musical instrument, a VCA circuit must be connected to an output of a sound source circuit, and a control circuit for controlling the control voltage input to the VCA circuit is also necessary. In general, the sound source circuit is digital-controlled by a CPU (central processing unit). However, the VCA circuit is an analog circuit. In order to control the VCA circuit, a D/A (digital-to-analog) converter is required. As a result, the circuit is complicated, and cost is increased.
When the fader with the motor is used in a volume control system, since the system includes a mechanically operating portion, maintenance is required.
When an operator wants to produce effect tones before a performance begins, begin the performance thereafter, and fade out the effect tones during the performance, he or she must perform complicated switching operations, and cannot concentrate on the performance.